1. Field of the Invention
The present invention relates to an image forming apparatus for forming an image on a recording medium, and more particularly to an image forming apparatus capable of recovering a sheet jam by releasing a fixing apparatus from a body of the image forming apparatus in conjunction with a sheet conveying apparatus.
2. Discussion of the Background
In an image forming apparatus, such as a copier, printer, facsimile, etc., a type of forming a latent image on a recording medium (herein after referred to as a sheet) and developing the latent image with toner, fixing the toner image, and ejecting the sheet has been widely spread as a known art. In such an image forming apparatus, a tip of the sheet occasionally contacts a member adjacent to a sheet conveying path and is lodged there thereby becoming jammed during its conveyance. This phenomenon is generally called xe2x80x9cJAM,xe2x80x9d and is not absolutely avoidable as far as a sheet is conveyed. In particular, such a jam tends to occur in the vicinity of a fixing section of the image forming apparatus.
Further, an apparatus configured to form an image on both sides of a sheet has been known. In a conventional both sides recordable (i.e., duplex) image forming apparatus, an image (i.e., a visualized image) formed on the image carrier is typically transferred and fixed onto the sheet. Then, the sheet is inverted by an inverting path or the like, and fed again so that the other image (a visualized image) can be transferred onto its rear side and fixed.
In such a duplex recording system, a bifurcation or inversion path necessarily is positioned downstream of a fixing device in a sheet conveying direction and operates after an image is fixed on one side (a first side). For example, a duplex copier disclosed in Japanese Utility Model Application Laid Open No. 5-64174 includes a conveyance path switching lever arranged downstream of a fixing roller in the sheet conveying direction between conveyance and ejection rollers. In addition, an intermediate tray unit is arranged further downstream thereof.
However, such an apparatus that transfers and fixes an image onto a backside of a sheet after inverting the sheet raises problems of credibility due to causing sheet curl after fixation of one side image and a long inversion path. Further, owing to a layout of a bifurcation pick, inverting path located downstream of the fixing apparatus in the sheet conveying direction, and apparatus, such as a conveyance apparatus disposed in an upper side, scanning apparatus, etc., the fixing apparatus can be withdrawn only in a direction perpendicular to a sheet conveyance direction along the sheet plane (i.e., in a direction perpendicular to a sheet plane of FIG. 1 of the above-described publication)
Thus, if a jam that occurred in the fixing apparatus is recovered, and the fixing apparatus is moved in a direction perpendicular to the sheet conveyance direction along the sheet plane, the jam sheet is torn and partially remains due to a relative movement such as lateral deviation of either the ejection or transferring and conveying apparatus from the fixing apparatus.
In view of the above-described problem, the present invention attempts to suppress tearing and a jam sheet partially remaining in a fixing apparatus or other sections when a jam that occurred in a fixing section is to be recovered in a duplex image forming apparatus.
Further, several proposals have been advanced for efficiently recovering a jam with superior operationality. For example, Japanese Patent Application Laid Open No. 2000-44086 refers to a structure in which a motion an upper cover to be open is transmitted to idle, fixing, and ejection rollers collectively serving as a sheet conveyance device by a gear, pinion, and rack collectively serving as a transmission device so as to drive these rollers when a jam occurs, so that a jam sheet is fed and recovered.
Further, Japanese Patent Application Laid Open No. 9-101732 refers to a structure in which an image forming apparatus is divided into two pieces. Specifically, a guide member and guide roller are provided in the first body that houses an image exposure device, sheet feeding section, and fixing apparatus or the like, and is engaged with a plate like member and rotational roller of the second body that houses a photoconductive member, charger, developing device, and cleaning apparatus or similar device. Thus, the Japanese Patent Application Laid Open No. 9-101732 discloses a construction in which an image transfer zone and sheet conveyance surface can be open without an exposure surface of the PC member being exposed by moving the second body arranged upstream in a sheet feeding direction when a jam sheet is to be recovered.
Further, Japanese Patent Application Laid Open No. 2000-198579 refers to a structure in which when a jam occurs in a sheet conveyance path, an operator is urged to confirm a condition of an interior of the fixing apparatus by continuously displaying a jam message until the fixing apparatus is once detached.
However, there exists a type of a jam sheet not fed and recovered when a roller is only driven. For example, when a fixing separation pick sticks into a jam sheet, and the jam sheet is forcibly conveyed, a fixing roller is occasionally damaged and is rendered to be unrecovable. The technology proposed by Japanese Patent Application Laid Open No. 2000-44086 cannot fix such a jam type.
Further, the construction of Japanese Patent Application Laid Open No. 9-101732 can indeed overlook the entire conveyance section. However, Japanese Patent Application Laid Open No. 9-101732 needs a great deal of a withdrawal distance, and the apparatus itself requires a complicated structure. As a result, the cost increases. The continuous jam display of Japanese Patent Application Laid Open No. 2000-198579 is efficient in view of confirmation of a jam sheet. However, it is not directed to an improvement in the operationality of jam recovery.
Further, the conventional duplex copier necessarily includes a sheet-inverting path, which is not opened in conjunction with a body cover at a time of sheet jam.
The present invention has been made in view of such problems and to address and resolve such problems.
Accordingly, an object of the present invention is to provide a duplex image forming apparatus including a first image carrier configured to carry a first image, and a second image carrier configured to receive the first image. The first image is transferred to one side of a recording medium from the second image carrier, and a second image is formed on the first image carrier and transferred to the other side of the recording medium. Also included is a recording medium conveying device configured to vertically convey the recording medium to a fixing section along a vertical conveyance path at least starting from where the first and second images are transferred onto the recovery medium, and a fixing device included in the fixing section configured to simultaneously fix the first and second images to respective sides of the recording medium. Further, the fixing device is released in conjunction with the recording medium conveying device when the recording medium conveying device is swung and released from the image forming apparatus body such that a portion of the vertical conveyance path extending upstream of the fixing device is opened.